The invention is directed to a cooling means for components that are situated in a vacuum chamber for the purpose of function testing with focused electron or ion beams.
For the purpose of an internal analysis, electronic components are electrically operated in the evacuated testing chamber in electron beam measuring instruments, scanning electron microscopes, or focused ion beam apparatus.
Such an electron beam measuring instrument is described in the brochure of the Schlumberger Company "Technologies IDS 4000 Integrated Diagnostics System", August 1988, incorporated herein, with which it is possible to quickly and precisely identify faults in integrated circuits or printed circuit boards.
Its fundamental structure is shown in FIG. 1. The vertically arranged opto-electronic column 8 that generates the electron beam is held at a receptacle frame 9 that simultaneously contains an adjustment system 7 that allows a displacement of the column 8 in the horizontal XY-plane. The overall apparatus is situated in a cabinet that is part of a work station which is covered with a work plate 10. The unit 4 under test is situated in the inside of a vacuum chamber 12 that is accessible via the cover hood 2 that projects from the work plate 10. A mount 5 for the acceptance of the unit 4 under test is attached to the upper inside of the cover hood and the individual contacts of this mount are conducted in vacuum-tight fashion to the outside of the cover hood 2 by terminal pins 3. The opto-electronic column projects into the vacuum chamber 12 sealed with a bellows 13.
The heat arising due to the dissipated power can be eliminated from the chamber only by thermal conduction. Specifically given bipolar circuits having their dissipated powers up to 40 Watts, a considerable difference between junction temperature and ambient temperature arises, this making it more difficult to control the chip temperature.
The solution according to FIG. 2 and described in the afore-mentioned brochure shows a liquid-cooled metal block 14 that is mounted in the vacuum chamber 12 at the unit 4 under test and the opto-electronic column 8. The coolant is conducted toward the outside from the vacuum chamber 12 via hoses 15, 16.
The heat elimination occurs over the housing material that resides next to the active chip surface. In addition to the preparation problems that thus particularly arise for plastic-housed components, the heat transmission resistance of this solution is also relatively high. This solution cannot be realized at all for components in TAB mounting (tape automatic bonding). What is also disadvantageous about this solution is the necessity of introducing flow-traversed tubes into the vacuum chamber.